So, as you can see, when I add a few variables it doesn't work. Has someone experienced something similar or know how to fix this? Thanks in advance!

Regards,
aevirex

EDIT: Sorry for being so hastily. I asked this question in the Quakenet #opengl channel. The result I was told was to include the varying variable in the vertex shader as well. Again sorry, I should have spent more time with the GLSL specification before jumping to conclusions.